离子液体缓蚀剂缓蚀机理的理论研究

发布时间：2018-09-08 16:21

【摘要】：金属腐蚀普遍存在于国民经济、国防建设和科学技术等领域,其危害十分严重,有必要采取一定的防护措施。缓蚀剂作为一种简单有效的添加剂能有效地抑制金属的腐蚀,已成为一种最常用的防腐手段。离子液体因其分子中存在杂环结构、杂原子(如N、O、S)和多重键,成为潜在的良好缓蚀剂并已被应用于金属的防腐领域。近几年来已取得了不少进展,但目前离子液体缓蚀剂的研究主要集中在缓蚀性能和效率方面,对于缓蚀过程的微观机理研究较少。本文以三组体系(氯化1-烷基-3-甲基咪唑[XMIM][C1]体系,1-烷基-3-甲基咪唑乙酸盐[XMIM][Ac]体系和1-辛基-3-甲基咪唑盐[OMIM][Y]体系,其中X为乙基、丁基、己基和辛基,Y为Cl、BF4、HS04、Ac和TfO)共11种离子液体作为抑制低碳钢腐蚀的研究对象,采用量子化学计算的方法系统地分析了离子液体的电子结构和反应活性、铁表面的表面能和电子结构,采用分子动力学模拟的方法研究了离子液体在铁表面的吸附行为、揭示了缓蚀过程的微观机制。取得了如下研究成果:计算发现,对于同一阴离子不同阳离子的[XMIM][C1]和[XMIM][Ac]体系,随烷基链长的增加,最高占有轨道能量(EHOMO)、最低空轨道能量(ELUMO)、软度(5)和极化率(α)逐渐增大,能隙差(△E)、偶极矩(μ)、硬度(η)和亲电指数(ω)逐渐降低。在同一阳离子不同阴离[OMIM][Y]体系中,离子液体的量子化学参数差异较大,只有极化率(α)呈增大的趋势。Fe(100)、Fe(110)和Fe(111)面的表面能γ的大小顺序为γFe(111)γFe(100)γFe(110),说明Fe(110)面的结构最为致密、稳定。铁表面的3d轨道最为活泼。Fe(110)不仅易与离子液体的含氧阴离子相互作用,也能与离子液体阳离子的咪唑环相互作用。因此,选取Fe(110)面作为离子液体的吸附面。结果表明,对于[XMIM][C1]体系,起到缓蚀作用的主要是阳离子[XMIM]+,缓蚀效率的排序为[OMIM][Cl][HMIM][C1][BMIM][C1][EMIM][C1]。[XMIM][Ac]体系的阳离子[XMIM]+和阴离子Ac-均有缓蚀的作用,缓蚀效率的顺序为[OMIM][Ac][HMIM][Ac][BMIM][Ac][EMIM][Ac]。在[OMIM][Y]体系中,阳离子[XMIM]+和阴离子 BF4-、HSO4-、Ac-、TfO-均有缓蚀的作用,缓蚀效率的排序为[OMIM][TfO][OMIM][Ac][OMIM][HS04][OMIM][BF4][OMIM][C1]。无论哪种体系,均有离子液体的阳离子或阴阳离子吸附且覆盖在Fe(110)面形成一层保护膜,阻碍腐蚀介质(H2O、H3O+、Cl-)与金属表面相互作用,以达到缓蚀的目的。综上所述,[OMIM][TfO]是所研究11种离子液体中的最佳缓蚀剂。
[Abstract]:Metal corrosion is common in the fields of national economy, national defense construction, science and technology, and its harm is very serious, so it is necessary to take some protective measures. As a simple and effective additive, corrosion inhibitor has become the most commonly used anticorrosion method. Ionic liquids have been used as potential corrosion inhibitors because of their heterocyclic structure, heteroatoms (such as Nu OS) and multiplex bonds, and have been used in the field of metal corrosion protection. A lot of progress has been made in recent years, but at present, the research of ionic liquid corrosion inhibitor is mainly focused on the corrosion inhibition performance and efficiency, and the microscopic mechanism of the inhibition process is less studied. In this paper, three systems (1-alkyl-3-methylimidazole [XMIM] [C1] system) of 1-alkyl-3-methyl imidazole acetate [XMIM] [Ac] and 1-octyl -3-methyl imidazolium salt [OMIM] [Y] system, in which X is ethyl, Ding Ji, Eleven kinds of ionic liquids, hexyl and octyl (Cl,BF4,HS04,Ac and TfO), were used to inhibit corrosion of low carbon steel. The electronic structure and reaction activity of ionic liquids, surface energy and electronic structure of iron surface were systematically analyzed by quantum chemical calculation. The adsorption behavior of ionic liquids on iron surface was studied by molecular dynamics simulation, and the microscopic mechanism of corrosion inhibition process was revealed. The results are as follows: it is found that for [XMIM] [C1] and [XMIM] [Ac] systems with different cations of the same anion, with the increase of alkyl chain length, the maximum occupied orbital energy, (EHOMO), and the lowest orbital energy, (ELUMO), softness (5) and polarizability (伪), increase gradually. The energy gap difference (E), dipole moment 渭), hardness (畏) and electrophilic index (蠅) decreased gradually. The quantum chemical parameters of ionic liquids vary greatly in the same cationic [OMIM] [Y] system. Only the polarizability (伪) tends to increase. The order of surface energy 纬 of Fe (100) Fe (110) and Fe (111) surfaces is 纬 Fe (111) 纬 Fe (100) 纬 Fe (110), which indicates that the structure of Fe (110) surface is the most compact and stable. The 3D orbital on iron surface is most active. Fe (110) is easy to interact with not only the anion containing oxygen but also the imidazole ring of ionic liquid cationic. Therefore, the Fe (110) surface is selected as the adsorption surface of ionic liquids. The results show that for [XMIM] [C1] system, the inhibition efficiency is mainly cationic [XMIM], and the order of inhibition efficiency is [OMIM] [Cl] [HMIM] [BMIM] [C1] [EMIM] [C1] [EMIM] [C1]. [XMIM] [Ac] the order of inhibition efficiency is [OMIM] [Ac] [HMIM] [Ac] [BMIM] [Ac] [EMIM] [EMIM] [Ac]. The order of inhibition efficiency is [OMIM] [Ac] [HMIM] [Ac] [BMIM] [Ac] [EMIM] [EMIM] [Ac]. In [OMIM] [Y] system, both cation [XMIM] and anionic BF4-,HSO4-,Ac-,TfO- can inhibit corrosion. The order of inhibition efficiency is [OMIM] [TfO] [OMIM] [Ac] [OMIM] [HS04] [OMIM] [BF4] [OMIM] [C1]. In either system, cationic or anion ions of ionic liquids are adsorbed and covered on the surface of Fe (110) to form a protective film, which hinders the interaction between the corrosion medium (H _ 2O _ H _ 3O _ 3O _ (Cl-) and the metal surface in order to achieve the purpose of corrosion inhibition. In conclusion, [OMIM] [TfO] is the best corrosion inhibitor in 11 ionic liquids studied.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.42

【参考文献】